Design and calibration of unicapillary pneumotachographs.
This study presents a method for design and calibration of unicapillary pneumotachographs for small-animal experiments. The design, based on Poiseuille's law, defines a set of internal radius and length values that allows for laminar flow, measurable pressure differences, and minimal interference with animal's respiratory mechanics and gas exchange. A third-order polynomial calibration (Pol) of the pressure-flow relationship was employed and compared with linear calibration (Lin). Tests were done for conditions of ambient pressure (Pam) and positive pressure (Ppos) ventilation at different flow ranges. A physical model designed to match normal and low compliance in rats was used. At normal compliance, Pol provided lower errors than Lin for mixed (1-12 ml/s), mean (4-10 ml/s), and high (8-12 ml/s) flow rate calibrations for both Pam and Ppos inspiratory tests (P < 0.001 for all conditions) and expiratory tests (P < 0.001 for all conditions). At low compliance, they differed significantly with 8.6 +/- 4.1% underestimation when Lin at Pam was used in Ppos tests. Ppos calibration, preferably in combination with Pol, should be used in this case to minimize errors (Pol = 0.8 +/- 0.5%, Lin = 6.5 +/- 4.0%, P < 0.0005). Nonlinear calibration may be useful for improvement of flow and volume measurements in small animals during both Pam and Ppos ventilation.
Giannella-Neto
A
A
Biomedical Engineering Program, Graduate School of Engineering, Federal University of Rio de Janeiro, Brazil. agn@peb.ufrj.br
Bellido
C
C
Barbosa
R B
RB
Melo
M F
MF
D000818:Animals; D001274:Atmospheric Pressure; D002138:Calibration; D008170:Lung Compliance / Q000502:physiology; D008954:Models, Biological; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012121:Respiration, Artificial / Q000295:instrumentation / Q000592:standards; D012129:Respiratory Function Tests / Q000295:instrumentation* / Q000592:standards; D015656:Respiratory Mechanics / Q000502:physiology